Conduction Mechanism Study And Defect Level Analysis Of ?-Ga₂O₃ Single Crystal

Ga₂O₃ is a new fourth-generation wide-band-gap semiconductor material with a theoretical breakdown field strength up to 8 MV/cm.Ga₂O₃ is widely used in high-power electronic devices and deep ultraviolet detection.The lack of systematic research on the conductive mechanism and the deep and shallow defects not only limits the research steps of optical and electrical properties,but also restricts the performance improvement of power devices and UV detectors based on Ga₂O₃.In this paper,undoped Ga₂O₃?Ta:Ga₂O₃ and Nb:Ga₂O₃ were successfully grown through Floating Zone Method and Edge-Defined,Film Fed Growth Method.The optical and electrical properties were measured accurately by variable methods such as hall effect,X-ray photoelectron spectroscopy,deep level transient spectrum and photoluminescence.The conductivity mechanism,deep and shallow level defects and their relationship with the electrical and optical properties were analyzed based on measurement results.It includes the following parts:1?High quality unintentional doped Ga₂O₃,Nb:Ga₂O₃,Ta:Ga₂O₃ bulk single crystals were grown by optical floating zone method.The polishing parameters and the preparation process of ohm-contact electrode were studied.2?The unintentional doping Ga₂O₃ and Nb:Ga₂O₃ were measured by hall measurement system and physical property measurement system?PPMS?.The donor level and conduction mechanism were described by thermal activation transition model and nearest neighbor hopping model.The results showed that nearest neighbor hopping and Mott's variable range hopping can describe the carrier transport modes at low temperature and high temperature respectively.At the same time,it was found that the activation energy of Nb:Ga₂O₃ was 12-20 me V,significantly lower than that of undoped one?48.16 me V?and Si:Ga₂O₃ reported.3?X-ray photoelectron spectroscopy and Raman were used to measure the samples before and after annealing.The valence states and combination modes of Ga,O and C elements were quantitatively fitted.The influence mechanism of annealing in oxygen-containing-atmosphere on the electrical properties was analyzed and the effects of C element on the electrical properties was systematically described.4?Deep level defects were characterized by deep level transient spectrum and photoluminescence with temperature.The luminescence mechanism of the intrinsic ultraviolet band was analyzed.Nb:Ga₂O₃ sample was detected with three defects of 0.12e V,0.49 e V and 0.81 e V,while Ta:Ga₂O₃ samples were detected with two defects of 0.56e V and 0.7 e V.At the same time,the luminescence peak at 316 nm which was not found in other samples was detected in Nb:Ga₂O₃.Based on the results of DLTS and PL,the luminescence mechanism of ultraviolet band was preliminarily analyzed.